Method and system for controlling draw tension on thread in a sewing system

ABSTRACT

A method of controlling draw tension on thread wrapped around a bobbin that is mounted operatively on a case for movement relative to the case around an axis. The method includes the steps of: predetermining a desired thread draw tension to be achieved with the bobbin operatively mounted on a case using a predetermined mounting process; and, before operatively mounting the bobbin on the case, selectively controlling the at least one parameter of at least one of the thread and bobbin in a correlative manner to the desired thread draw tension with the bobbin operatively mounted on a case using the predetermined mounting process.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to sewing systems and, more particularly,to a method and system through which the draw tension on threadwithdrawn from a supply on a bobbin can be controlled.

[0003] 2. Background Art

[0004] Stitching operations in sewing systems are commonly carried outby continuously withdrawing thread from a wrapped supply thereof on abobbin. Typically, a bobbin case has a generally cylindricalconstruction and defines a receptacle within which the bobbin nests. Thebobbin case has a post which is directed through a core on the bobbin toguide rotational movement of the bobbin relative to the case. In atypical system design, thread departing from the bobbin is directedthrough an opening/slot in the peripheral wall of the case and engaged,as by a rotary loop taker, to be tensioned thereby and drawn off of thebobbin.

[0005] In operation, the bobbin is rotated at a relatively high speed.As the draw tension is removed, the momentum of the moving bobbin, withthe wrapped thread thereon, tends to cause the bobbin to continuerotating. In the absence of a resistive force on the bobbin, threadbacklash may result. To remedy this situation, it may be necessary tomanually untangle the line on the bobbin or, in an extreme case, cut thethread from the bobbin, and either replace the bobbin with a bobbin thatis pre-wound or rewind thread on the active bobbin. In any event, thebacklash problem potentially represents a loss in productivityattributable to system down time.

[0006] Various mechanisms have been devised to avoid the backlashproblem. The inventor herein has developed systems which generate aresistive force between the bobbin the case which avoids backlash, butdoes not significantly impair the rotation of the bobbin, as necessaryto withdraw thread during operations.

[0007] In one such system, a magnetic attractive/repulsive force isgenerated between parts of the bobbin and associated case to resistrotation therebetween. In another system, axially extending memberscooperate between the bobbin and case to frictionally produce a forcebetween the bobbin and case that resists rotation.

[0008] In addition to controlling backlash, draw tension is commonlyadjusted as a particular application may dictate. Thus, virtually allsewing systems incorporate a thread draw tension adjusting capability.One of the most commonly used systems employs a spring element whichcaptures the thread, at the point it departs radially through the caseopening/slot, against the radially outwardly facing surface of the case.The captive force on the thread is variable through an adjusting screwassociated with the spring element.

[0009] Another tension controlling/adjusting mechanism is shown in U.S.Pat. No. 6,152,057, commonly assigned with this invention. In thismechanism, thread departing from the case opening/slot is wrapped aroundan elongate rod. The draw resistance is dictated by the degree ofcontact between the thread and rod, which depends upon the diameter ofthe rod and the number of turns of thread therearound.

[0010] The process of setting the desired draw tension in conventionalsystems can be onerous. The draw tension is affected by many differentaspects of the sewing system. For example, the anti-backlashingstructure, as described above, produces a resistive force to rotationthat affects draw tension. Draw tension is further affected by, amongother things, the tack of the thread, the shape of the thread, thematerial defining the thread, the fiber make-up of the thread, thewrapping pattern of the thread on the bobbin, the wrapping tension ofthe thread around the bobbin, etc.

[0011] Heretofore, sewing systems have been designed so that thread drawtension is selectively adjusted by an operator through a mechanismseparate from the bobbin, once the bobbin is installed. In a typicalsewing system, numerous bobbin/case assemblies are simultaneouslyutilized. For each such bobbin/case assembly, individual draw tensionadjustments are carried out, as by adjusting a set screw and thereby thecaptive spring force against thread at the outside of the casing,controlling the wraps on the projecting rod, etc. This is normally doneon a trial and error basis, requiring potentially numerous preliminaryadjustments to be made on each of multiple bobbin/case assemblies beforeactual sewing operations can be carried out.

[0012] To the knowledge of the inventor herein, no effort has been madeby anyone in the industry to control all the different parameters thataffect thread draw tension in such a manner that using a simple,consistent, installation process for the bobbin, a resulting drawtension will predictably result. Instead, the industry has dealt withthe problem of time intensive system adjustment resulting from anuncontrolled selection of different combinations of parameters, i.e.,thread texture, thread tack, thread shape, etc., without coordinatinglychoosing these parameters for a predictable draw tension outcome. As aresult, those in the industry continue to make multiple adjustments oneach of multiple bobbin/case assemblies in their systems to controlthread draw tension. Each time a system change is made, such as thereplacement of one bobbin with another, the exercise of carrying outadjustments must be undertaken anew.

SUMMARY OF THE INVENTION

[0013] In one form, the invention is directed to a method of controllingdraw tension on thread wrapped around a bobbin that is mountedoperatively on a case for movement relative to the case around an axis.The method includes the steps of: predetermining a desired thread drawtension to be achieved with the bobbin operatively mounted on a caseusing a predetermined mounting process; and, before operatively mountingthe bobbin on the case, selectively controlling the at least oneparameter of at least one of the thread and bobbin in a correlativemanner to the desired thread draw tension with the bobbin operativelymounted on a case using the predetermined mounting process.

[0014] In one form, the step of controlling the at least one parameterinvolves controlling thread tack.

[0015] The step of controlling the at least one parameter may involvecontrolling thread gauge.

[0016] The step of controlling the at least one parameter may involvecontrolling material defining the thread.

[0017] The step of controlling the at least one parameter may involvecontrolling thread shape.

[0018] In one form, the thread has a plurality of fibers. The step ofcontrolling the at least one parameter may involve controllingstructural interaction of the fibers defining the thread.

[0019] The step of controlling the at least one parameter may involvedefining the bobbin so as to control a magnetic interaction of thebobbin and case that resists rotation of the bobbin relative to the casewith the bobbin operatively mounted on the case.

[0020] The step of defining the bobbin may involve controllingparameters of a metallic component on the bobbin to magneticallyinteract with an element on the case.

[0021] The step of defining the bobbin may involve controllingparameters of a magnetic element on the bobbin to magnetically interactwith at least one of (a) a metallic element and (b) a magnetic elementon the case.

[0022] The step of controlling the at least one parameter may involvedefining the bobbin so as to control frictional interaction of thebobbin and case that resists rotation of the bobbin relative to the casewith the bobbin operatively mounted on the case.

[0023] The step of defining the bobbin may involve selecting a materialdefining at least a part of the bobbin.

[0024] The step of defining the bobbin may involve providing a flexiblecomponent on the bobbin that is biasably urged against the case with thebobbin operatively mounted on the case.

[0025] The step of defining the bobbin may involve providing a surfacethat produces a frictional resistance to rotation when borne against bya flexible component on the case with the bobbin operatively mounted tothe case.

[0026] The step of controlling the at least one parameter may involvecontrolling the configuration of the bobbin.

[0027] In one form, thread is wrapped around the bobbin with a wrappingpattern and the step of controlling the at least one parameter involvescontrolling the wrapping pattern.

[0028] In one form, thread is wrapped around the bobbin with a wrappingtension and the step of controlling the at least one parameter involvescontrolling the wrapping tension.

[0029] The invention is further directed to a method of controlling drawtension on thread wrapped around a bobbin and mounted operatively on acase for movement relative to the case around an axis. The methodincludes the steps of: providing a first bobbin with a supply of threadwrapped around the first bobbin so that with the first bobbinoperatively mounted on a first case using a predetermined mountingprocess, a first thread draw tension results; providing a second bobbinwith a supply of thread wrapped around the second bobbin so that withthe second bobbin operatively mounted on the first case using thepredetermined mounting process, a second thread draw tension differentthan the first thread draw tension results; choosing a desired threaddraw tension by selecting to operatively mount to the first case one ofthe first and second bobbins; and operatively mounting the one of thefirst and second bobbins to the first case.

[0030] The method may further include the step of predeterminingapproximately first and second magnitudes of thread draw tensionresulting with each of the first and second bobbins operatively mountedon the first case using the predetermined mounting process, andidentifying the first and second magnitudes to facilitate selection by auser of one of the first and second bobbins for use.

[0031] The invention is further directed to combination of a first andsecond bobbin. The first bobbin has a supply of a first thread wrappedaround the first bobbin so that with the first bobbin operativelymounted upon a case having a first construction using a predeterminedmounting process, a thread draw tension with a first magnitude results.The second bobbin has a supply of thread wrapped around the secondbobbin so that with the second bobbin operatively mounted upon a casehaving the first construction using the predetermined mounting process,a thread draw tension, with a magnitude of predetermined tensionpredetermined to be greater or less than the first magnitude, results.The first and second bobbins, with their respective thread supplies, canbe selectively operatively mounted upon a case having the firstconstruction to select greater or lesser thread draw tension.

[0032] The combination may further include a first case having the firstconstruction upon which the first and second bobbins can beinterchangeably operably mounted.

[0033] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in tack on the first and second threads.

[0034] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in gauge of the first and second threads.

[0035] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in material defining the first and second threads.

[0036] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in shape of the first and second threads.

[0037] The first and second threads may each be defined by a pluralityof fibers. The difference between a thread draw tension resulting fromthe mounting of the first and second bobbins with their respectivethread supplies to a case having the first construction may beattributable to at least a difference in structural interaction offibers defining the first and second threads.

[0038] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in magnetic interaction between a case having thefirst construction and the first and second bobbins.

[0039] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in a frictional interaction between the casehaving the first construction and the first and second bobbins.

[0040] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in configuration of the first and second bobbins.

[0041] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in wrapping pattern of the first and secondthreads around the first and second bobbins.

[0042] The difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction may be attributable toat least a difference in a wrapping tension for the first and secondthreads around the first and second bobbins.

[0043] In one form, the first bobbin has a first flange with aperipheral edge and the second bobbin has a second flange with a secondperipheral edge, each of which face a radially inwardly facing surfaceon a case having a first construction to which the first and secondbobbins are selectively operatively mounted. A difference between threaddraw tension resulting from the mounting of the first and second bobbinswith their respective thread supplies to a case having the firstconstruction is attributable to at least a difference in interaction ofthe first and second peripheral edges with the radially inwardly facingsurface on the case having the first construction, to which the firstand second bobbins are operatively mounted.

[0044] The invention is further directed to the combination of a caseand a bobbin. The case has a radially inwardly facing surface extendingaround a space. The bobbin has an axis and a first axially facing flangewith a peripheral edge facing the radially inwardly facing case surface.The case and bobbin are configured so that the peripheral edge of theflange does not contact the radially inwardly facing surface of the casearound the entire peripheral edge.

[0045] In one form, the case and bobbin are configured so that theperipheral edge of the flange does not contact the radially inwardlyfacing surface of the case.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046]FIG. 1 is a schematic representation of a sewing system, includinga case to which bobbins with thread supplies thereon can be selectivelymounted to select an operating thread draw tension, according to thepresent invention;

[0047]FIG. 2 is a partially schematic representation of the sewingsystem in FIG. 1 and showing in cross section the case with one of thebobbins, with its associated thread supply, operatively mounted thereon;

[0048]FIG. 3 is an exploded perspective view of side-walled bobbins thatcan be interchangeably mounted to the case in FIG. 2, according to thepresent invention;

[0049]FIG. 4 is an enlarged, fragmentary, elevation view of one form offrictional element for controlling thread draw tension on the sewingsystem in FIGS. 1 and 2;

[0050]FIG. 5 is a view as in FIG. 4 of another form of friction elementfor controlling thread draw tension;

[0051]FIG. 6 is a view as in FIG. 3 wherein the interchangeable bobbinshave a sideless construction;

[0052]FIG. 7 is an enlarged, cross-sectional view of one thread to beused on the bobbins of FIGS. 2, 3 and 6 and having a tack compositionthereon;

[0053]FIG. 8 is a view as in FIG. 7 wherein the tack composition has adifferent thickness;

[0054]FIG. 9 is a cross-sectional view of one thread to be used on thebobbin, and having a first gauge;

[0055]FIG. 10 is a view as in FIG. 9 with the thread having a differentgauge;

[0056]FIG. 11 is a cross section of one thread to be used on the bobbinsof FIGS. 2, 3, and 6 and having a squared cross-sectional shape;

[0057]FIG. 12 is a view as in FIG. 11 wherein the shape is oval;

[0058]FIG. 13 is a view as in FIGS. 11 and 12 wherein the shape isround;

[0059]FIG. 14 is a view as in FIGS. 11-13 wherein the shape is flat;

[0060]FIG. 15 is a fragmentary, elevation view showing magnetic elementscooperating between the case and flanges on the bobbins in FIGS. 2 and3;

[0061]FIG. 16 is a view as in FIG. 15 with a different arrangement ofmagnetic elements;

[0062]FIG. 17 is a fragmentary, cross-sectional view cooperatingportions on the bobbins and case in FIG. 6, wherein magnetic particlesare dispersed to produce a magnetic attractive force between the bobbinsand case;

[0063]FIG. 18 is a view as in FIG. 17 wherein the concentration of themagnetic particles is different than that in FIG. 17;

[0064]FIG. 19 is a view as in FIG. 15 wherein flexible elementsprojecting from one of the case and bobbins is biased frictionallyagainst the other of the case and bobbins to retard relative rotationbetween the case and bobbins;

[0065]FIG. 20 is a view as in FIG. 19 wherein the flexible elements havea different configuration so as to have different bending and frictionalcharacteristics;

[0066]FIG. 21 is a schematic representation of one winding pattern forthread around the bobbins in FIGS. 3 and 6; and

[0067]FIG. 22 is a view as in FIG. 21 showing another form of wrappingpattern for the thread around the bobbins;

[0068]FIG. 23 is a fragmentary, cross-sectional view of one of thebobbins in FIG. 3 operatively mounted on the case;

[0069]FIG. 24 is a plan view of an alternative form of bobbin, accordingto the invention, operatively mounted on a case that is shown inschematic form; and

[0070]FIG. 25 is a fragmentary, plan view of a further modified form ofbobbin and having a projection therefrom to control contact between thebobbin and a case to which the bobbin is operatively mounted.

DETAILED DESCRIPTION OF THE DRAWINGS

[0071] In FIG. 1, a sewing system is shown at 10 incorporating akit/combination of components 12, according to the present invention.More specifically, the system 10 consists of a case 14 upon which firstand second bobbins 16,18, respectively, are selectively, operativelymounted. The bobbin 16 has a first thread supply 20 with the bobbin 18having a second thread supply 22 wrapped therearound. Thread 20, 22 fromthe operative bobbin 16,18 is drawn off of the bobbin through a threaddrawing mechanism 24, that may be a rotary loop taker, or the like.

[0072] According to the invention, with the first bobbin 16 and itsthread supply 20 operatively mounted upon the case 14 using apredetermined mounting process, a first magnitude of thread draw tensionresults as thread 20 is withdrawn from the bobbin 16 through the threaddrawing mechanism 24. With the second bobbin 18 and its thread supply 22operatively mounted upon the case 14 using the predetermined mountingprocess, the magnitude of the thread draw tension is either greaterthan, or less than, the first magnitude. Accordingly, the first andsecond bobbins 16,18, with their respective thread supplies 20,22, canbe selectively operatively mounted upon the case 14 to preselect agreater or lesser thread draw tension. Preferably, the magnitude of thethread draw tension, resulting with each of the bobbins 16,18 with itsrespective thread supply 20,22 operatively mounted upon the case 14, iseither approximately or accurately predetermined. Accordingly, the usercan, within a range, predetermine and thus select, a desired thread drawtension that results using the bobbins 16,18 with their respectivethread supplies 20,22.

[0073] The difference in the thread draw tensions resulting from theselection of the bobbins 16,18 is attributable to a variation in atleast one parameter of at least one of the thread 20, 22 and bobbins 16,18. Before these different parameters are discussed, a more detailedexplanation of the sewing system 10 will be made, initially with respectto FIGS. 2 and 3.

[0074] The sewing system 10 in FIGS. 2 and 3 utilizes side-walledbobbins 16,18. The case 14 has a base wall 28 with a peripheral wall 30extending upwardly therefrom to bound, in conjunction with the base wall28, a cylindrical thread storage space 32. The case 14 is mounted upon aframe 34 in a conventional manner. A hollow post 36 projects upwardlyfrom the base wall 28 and has a central axis 38. The post 36 has acylindrical outer surface 40 which is journalled for rotation in bores42,44 through the bobbins 16,18, respectively. With the bobbins 16,18operatively mounted on the case 14, as shown in FIG. 2, the bobbins16,18 are rotatable about the central axis 38 of the hollow post 36.

[0075] The bobbin 16 has axially spaced flanges 46,48 which are attachedat the ends of a cylindrical core 50. The flanges 46,48 have axiallyfacing surfaces 52,54 which determine the thread volume capacity for thebobbin 16. The thread supply 20 is wrapped around the core 50 in thespace between the flange surfaces 52,54.

[0076] The bobbin 18 has flanges 56,58 at the axial ends of a core 60.The flanges 56,58 have axially facing surfaces 62,64 which bound a spacefor the thread 22 wrapped around the core 60.

[0077] With the active bobbin 16,18 operatively mounted on the case 14,the thread 20,22 is directed through a radial opening/slot 66 throughthe case wall 30 in a radial direction to be engaged by the threaddrawing mechanism/rotary loop taker 24.

[0078] It is known to control draw tension on the thread 20,22 through afriction element, shown generically at 68 in FIG. 2, and acting againstthe thread 20,22 as it paid off of the bobbins 16,18. One suitablefriction element 68 is construction as shown in FIG. 4 in the form of aleaf spring 72 which is mounted to the peripheral wall 30 of the case 14and maintained in place by one or more screws 76. The thread 20,22 thatdeparts from the wall opening/slot 66 is captively situated between theleaf spring 72 and the peripheral wall 30. By adjusting the screw(s) 76,the captive force upon the exiting thread 20,22 can be changed to eitherincrease or decrease draw tension on the thread 20,22.

[0079] In an alternative form of friction element 68′, as shown in FIG.5, an elongate, cantilevered element 78 projects from the peripheralwall 30, as shown in U.S. Pat. No. 6,152,057, the disclosure of which isincorporated herein by reference. The draw tension for the thread 20,22is variable by changing the degree of wrapping of the thread 20,22around the cantilevered element 78, as described more fully in U.S. Pat.No. 6,152,057.

[0080] A modified form of bobbin construction is shown in FIG. 6 and isknown in the industry as a sideless bobbin. The invention alsocontemplates practice thereof using sideless bobbins 16′,18′,corresponding to the bobbins 16,18, previously described, in combinationwith a case 14, as previously described, to include the base wall 28,peripheral wall 30 and hollow post 36 with the central axis 38. Theperipheral wall 30 bounds the thread storage space 32.

[0081] The bobbins 16′,18′ have through bores 42′,44′ to receive thecylindrical outer surface 40 of the hollow post 36 with the bobbins 16′,18′ operatively mounted on the case 14. The thread 20,22 is wrappedaround the outer surfaces 80,82, which function as the aforementionedcores 50,60 on the bobbins 16,18.

[0082] The above description is intended to provide potentiallydifferent environments in which the present invention can be practiced.The invention can be practiced in virtually any type of sewing system inwhich thread-carrying bobbins can be interchangeably mounted upon acase. In fact, the invention can actually be practiced by changing atleast one parameter of at least one of the thread and bobbin whichremains operatively mounted upon a case. Certain, but not all, of theparameters of the thread 20, 22 and the bobbins 16,18,16′,18′ that canbe varied, according to the present invention to control thread drawtension in a predetermined manner, are described below.

[0083] It is known that the degree of tack on thread affects the drawtension using the conventional bobbin/case combination. As shown in FIG.7, the thread 20 is shown with a tack composition 84 coated on itsexposed, outer surface 86. In FIG. 8, a tack composition 84′ is coatedon the outer surface 86 of the thread 22. In FIG. 8, the radialthickness T of the tack composition 84 is greater than the correspondingthickness T1 of the tack composition 84 in FIG. 7.

[0084] The magnitude of the draw tension resulting from the use of thethreads 20, 22 with the different tack composition thickness can bepredetermined approximately, or relatively precisely, for a givenconstruction of the case 14 and using a predetermined mounting processfor the bobbins 16,18,16′,18′ upon the case 14. For example, it can bepredetermined approximately, or exactly, what magnitude of draw tensionwill result using the different tack composition thicknesses T, T1 usingthe case 14 with a single wrap around the friction element 68′ in FIG.5. The operator can be provided with a simple setup routine which allowsa desired thread tack tension to be nominally, or relatively accurately,selected, by picking a bobbin 16,18,16′,18′ from a supply of the bobbins16,18,16′,18′ having the different tack composition thicknesses, with apredetermined correlation to different thread draw tensions, andoperatively mounting the same on the case 14 using the predeterminedmounting process. It is also contemplated that one or more additionalbobbins 16,18,16′,18′ could be provided with further different tackcomposition thicknesses correlated to additional thread draw tensions.

[0085] In addition to altering the thickness of the tack composition tocause different thread draw tensions to result, the supply of bobbins16,18,16′,18′, from which user selection can be made, may have differenttack compositions at the same or different thicknesses. As a furtheroption, one of the bobbins 16,18,16′,18′ could have thread 20,22 woundtherearound with no tack component, with another bobbin 16,18,16′,18′having thread 20,22 wound thereon with tack component which accounts fora greater thread draw tension compared to the thread 20,22 with no tackcomponent thereon.

[0086] An additional thread parameter that might be variably controlledis thread gauge. As shown in FIGS. 9 and 10, the thread 20 on the firstbobbin 16,16′ may have a first gauge, with the thread 22 on the secondbobbin 18,18′ having a second, larger gauge. This difference in gaugeaccounts for a different thread draw tension with the threads 20,22wrapped around the bobbins 16,16′ and 18,18′ and the bobbins16,18,16′,18′ operatively mounted on the case 14 using the samepredetermined mounting process.

[0087] Another thread parameter that is variable to change thread drawtension is thread shape, which is explained relative to FIGS. 11-14. InFIG. 13, the thread 20,22 is shown with a round shape. The thread 20,22could be formed with an elliptical shape, as shown in FIG. 12, a squaredshape as shown in FIG. 11, or a flattened state, as shown in FIG. 14.With the thread 20,22 wrapped around the bobbins 16,18,16′,18′, andthese bobbins 16,18,16′,18′ operatively mounted on the base 14 using apredetermined mounting process, different predeterminable thread drawtensions result.

[0088] As seen in FIG. 13, the threads 20,22 are made from a pluralityof fibers 90. The nature of the fibers 90 defining the threads 20,22 isanother parameter that can be varied to change thread draw tension.Further, the structural interaction of the fibers 90, be it the mannerin which they are bundled or wrapped, can likewise be controlled to varyresulting thread draw tension. The thickness of the fibers 90 for agiven gauge thread 20,22 can likewise be varied.

[0089] It is also known to produce a magnetic attractive/repulsive forcebetween the bobbins 16,18, and case 14 to produce a variable rotationalresistance force. As shown in FIG. 15, magnetic elements 94 can beprovided on the case 14 and/or bobbins 16,18, on either an axiallyfacing flange surface 96 or axially facing case surface 98. The surface96,98 confronting the magnetic elements 94 may be metallic to produce anattractive force which resists rotation between the case 14 and bobbins16, 18 to thereby cause an increase in the thread draw tension.Alternatively, magnetic elements 100 can be provided to cooperate withthe magnetic elements 94 and produce a repulsive force which resistsrotation between the case 14 and bobbins 16,18, so as to cause anincrease in thread draw tension.

[0090] In FIG. 15, multiple magnetic elements 94 and potentiallymultiple cooperating magnetic elements 94,100 are shown. In FIG. 16, thesame arrangement of magnetic elements 94/94,100 is used but with aresulting lesser magnetic force, either repulsive or attractive,produced between the case 14 and bobbins 16,18. Thus, one of the bobbins16 can be designed to be magnetically attracted/repelled to/from thecase 14 with a different force than the other of the bobbins 18.

[0091] A variable magnetic attractive force between the case 14 andbobbins 16′,18′ can be generated using an arrangement as shown in FIGS.17 and 18. Magnetic particles 104 are dispersed in either the post 36 onthe case 14 or on the bobbins 16′,18′ so as to produce an attractiveforce between the post 36 and bobbins 16′,18′ which resists rotationbetween the bobbins 16′,18′ and the case 14. The concentration of theparticles 104 is less in the bobbin 18′ than in the bobbin 16′ so as toproduce different rotational resistance forces.

[0092] The rotational resistance forces can be controlled/varied byusing different metal compositions for the bobbins 16′, 18′ which wouldbe attracted differently to the magnetic particles 104 on the case post36. Also, magnetic particles 104 can be provided in both the post 36 andbobbins 16′,18′ to produce a repulsive force that resists rotationbetween the case 14 and bobbins 16′,18′. The concentration of themagnetic particles 104 in both the post 36 and bobbins 16′,18′ can bechanged to produce the range of desired, predeterminable thread drawtensions with the bobbins 16′,18′ operatively mounted on the case 14.This same concept can be produced with the bobbins 16, 18, describedabove.

[0093] The inventor herein has also designed a rotation retardingmechanism using flexible, friction generating components on one of thecase 14 and bobbins 16,18, which bear against the other of the case 14and bobbins 16,18. As shown in FIG. 19, flexible elements 106 projectfrom one of the surfaces 96,98, identified in FIGS. 15 and 16, to bepressed biasably against the other surface 98,96. As show in FIG. 20,flexible elements 108, functioning in like manner, are provided and havea more rigid construction to have different bending and frictionalcharacteristics than the flexible elements 106. Accordingly, differentthread draw tensions result from the use of the flexible elements106,108 on bobbins 16,18 that are mounted upon the case 14.

[0094] It is also contemplated that part, or all, of the cooperatingsurfaces on the case 14 and bobbins 16,18,16′,18′, could be made fromdifferent materials to account for different thread draw tension. Forexample, the first bobbins 16,16′ could be made with surfaces, thatcontact the case 14, made from one material having first frictionalcharacteristics, with the same surfaces on the second bobbin 18, 18′made from a different material than that of the first bobbins 16,16′ andhaving different frictional characteristics so as to account fordifferent thread draw tensions with the bobbins 16,16′;18,18′ mountedoperatively upon the case 14. The texture of the cooperating surfaces onthe case 14 and bobbins 16,16′,18,18′ can also be changed to achievethis same end.

[0095] The frictional interaction of the bobbins 16, 16′, 18, 18′ may becontrolled by treating a surface on the bobbin 16, 16′, 18, 18′, orinterposing an element or a composition between the bobbins 16, 16′, 18,18′ and case 14. As one example, cardboard may be used to define one ormore of the flanges 46, 48, 56, 58 on one or more of the availablebobbins 16, 16′, 18, 18′. The cardboard can be treated, as byimpregnation with a lubricant, such as silicone, or the like. A coatingmight be applied to cardboard, or other material on the bobbin 16, 16′,18, 18′, such as a wax material.

[0096] As a further alternative, a lubricant might be appliedselectively to one or both surfaces on the case 14 and or bobbin 16,16′, 18, 18′ which move guidingly against one another during operationof sewing system 10. A silicone lubricant is an exemplary lubricantsuitable to control thread draw tension resulting with the bobbin 16,16′, 18, 18′ operatively mounted on the case 14.

[0097] Another parameter that may be varied is the thread wrappingpattern. As shown in FIGS. 21 and 22, the threads 20,22 can be wrappedaround the bobbins 16,16′,18,18′ in a pattern extending substantiallyorthogonal to the central axis 110 of the bobbins 16,16′,18,18′, asshown in FIG. 21, or in a bias pattern, as shown in FIG. 22. Thesepatterns are only exemplary of the many different patterns that might beused.

[0098] Further, the wrapping tension for the thread 20,22 can be variedfrom one bobbin 16,16′,18,18′ to the next to account for a variablethread draw tension.

[0099] Still further, by using different configurations of the bobbins16,16′,18,18′ in the selectable group, different, desired thread drawtensions can be arrived at. As one example, the different configurationsof the bobbins can have a different relationship between the outer edges114, 116, respectively, on the flanges 45, 48 on the exemplary bobbin 16and the radially inwardly facing surface 118 of the case 14, as seen inFIG. 23. In actuality, there is a slight radial gap D that existsbetween the radially inwardly facing surface 120 bounding the bore 42through the bobbin 16 and the outer post surface 40. There is likewise aradial gap D1 between the flange edge 114 and the case surface 118 and aradial gap D2 between the flange surface 116 and the case surfaces 118.By controlling the dimensions D1, D2, D3, the interaction between thebobbin 16 and case 14 can be selectively controlled so that a) thebobbin 16 cannot shift within the space 32 bounded by the case 14sufficiently to allow either flange edge 114, 116 to contact the casesurface 118, b) the bobbin 16 can shift radially so that one of the twoflange edges 114, 116 can contact the case surface 118, and c) thebobbin 16 can shift radially so that both of the flange edges 114, 116can contact the case surface 118. Thus, different configurations ofbobbin 16, 18 can be developed with which there is potentially a) nocontact permitted between the flange edges 114, 116 and the case surface118, b) contact by one or both of the flange edges 114, 116 and the casesurface 118, and c) variable degrees of contact force between one orboth of the flange edges 114, 116 and the case surface 118, all of whichconditions account for different thread draw tensions with the bobbins16, 18 operatively mounted on the case 14.

[0100] The configuration of the bobbins 16, 18 may be changed, from oneto the next, by altering the peripheral shape of one or both of theflange edges 114′, 116′, as shown in FIG. 24. As seen in FIG. 24, theflange edges 114′, 116′ have a polygonal shape which results in therebeing a number of circumferentially spaced, discrete locations at A, B,C, D, E at which there is point contact between the representativebobbin 16″ and the case surface 118. The polygonal shape shown toachieve this result is only exemplary. To vary the thread draw tensionresulting from the operative mounting of different bobbins 16″, thenumber, or shape of the contact locations, could be controlled/varied.

[0101] A similar effect can be produced by forming discrete radialprojections 124 on the representative flange 46 of the bobbin 16, as byembedding a separate element 125 therein. Alternatively, the projections124 could be formed as one piece with the flange 46.

[0102] It has been found that by eliminating the contact, or the contactarea, between the bobbin flange outer edges 114, 116 and case surfaces118, for a given bobbin setup with a particular set of parameters,thread draw tension fluctuation is unexpectedly constant as a supply ofthread 20 is exhausted therefrom. In conventional bobbin designs,contact between the outer edges 114, 116 and case surface 118 isanticipated substantially continuously since the bobbin is urgedradially outwardly due to centrifugal forces thereon and the carriedsupply of thread. To achieve the improved effect, the radial dimensionon a conventional bobbin flange may be reduced by design, or alteredafter manufacture, to diminish contact between the flange edges 114, 116and case surface 18 altogether, or reduce the contact area or contactpressure between the flange edges 114, 116 and case surface 118. Asidefrom controlling fluctuation in the thread draw tension for a particularbobbin over the operating period during which a supply of thread thereonis exhausted, this concept can be used to provide a plurality of bobbinsselectively usable to cause different predetermined thread draw tensionsto result with the bobbins operatively mounted on a case.

[0103] Other variations in configuration of the bobbins are contemplatedby the present invention. As just one other example, the configurationmay be changed to control in different manners the way in which threadis paid off of the bobbin. Virtually any change in shape that produces achange in which thread is paid off, or the bobbin interacts with a caseto which it is operatively mounted, are contemplated by the presentinvention.

[0104] It is contemplated that at least two bobbins 16,16′,18,18′, andpotentially a multitude of bobbins 16,16′,18,18′, could be madeavailable with different parameters for the bobbins 16,16′,18,18′ and/orthe thread 20,22 wrapped therearound. That is, a single parameter, ortwo or all of the above-described parameters, may be varied to producedesired alternative thread draw tensions with the bobbins 16, 16′, 18,18′ operatively mounted in the case using a predetermined mountingprocess. As noted above, the thread draw tension resulting fromincorporation of any of the plural bobbins 16,16′,18,18′ with the variedbobbin/thread parameters can be identified to the user with approximate,or precise thread draw tensions predetermined to result from operativemounting of that particular bobbin 16,16′,18,18′ on a case using apredetermined mounting process. As a result, once the user ascertainswhich thread draw tension is desired, a bobbin 16,16′,18,18′ capable ofcausing the desired thread draw tension can be selected and operativelymounted upon the case 14 following routine mounting steps. Accordingly,gross, and potentially even fine, adjustments at each bobbin/casecombination can be avoided. The particular bobbins 16,16′,18,18′ can bemarked and grouped either by gross ranges of thread draw tension whichthey will cause or by more precise thread draw tensions which they willaccount for if operatively mounted to the case 14 using a predeterminedmounting process.

[0105] Further, in a basic system that does not incorporate a threaddraw tension adjustment capability, into the case, predeterminableadjustment can be achieved by strategically using bobbins withparameters controlled/varied, as described above.

[0106] While the invention has been described with particular referenceto the drawings, it should be understood that various modificationscould be made without departing from the spirit and scope of the presentinvention.

1. A method of controlling draw tension on thread wrapped around abobbin that is mounted operatively on a case for movement relative tothe case around an axis, the method comprising the steps of:predetermining a desired thread draw tension to be achieved with thebobbin operatively mounted on a case using a predetermined mountingprocess; and before operatively mounting the bobbin on the case,selectively controlling at least one parameter of at least one of thethread and bobbin in a correlative manner to the desired thread drawtension.
 2. The method of controlling draw tension on thread accordingto claim 1 wherein the step of controlling the at least one parametercomprises controlling thread tack.
 3. The method of controlling drawtension on thread according to claim 1 wherein the step of controllingthe at least one parameter comprises controlling thread gauge.
 4. Themethod of controlling draw tension on thread according to claim 1wherein the step of controlling the at least one parameter comprisescontrolling material defining the thread.
 5. The method of controllingdraw tension on thread according to claim 1 wherein the step ofcontrolling the at least one parameter comprises controlling threadshape.
 6. The method of controlling draw tension on thread according toclaim 1 wherein the thread comprises a plurality of fibers and the stepof controlling the at least one parameter comprises controllingstructural interaction of the fibers defining the thread.
 7. The methodof controlling draw tension on thread according to claim 1 wherein thestep of controlling the at least one parameter comprises defining thebobbin so as to control a magnetic interaction of the bobbin and casethat resists rotation of the bobbin relative to the case with the bobbinoperatively mounted on the case.
 8. The method of controlling drawtension on thread according to claim 7 wherein the step of defining thebobbin comprises controlling parameters of a metallic component on thebobbin to magnetically interact with an element on the case.
 9. Themethod of controlling draw tension on thread according to claim 7wherein the step of defining the bobbin comprises controlling parametersof a magnetic element on the bobbin to magnetically interact with atleast one of (a) a metallic element and (b) a magnetic element on thecase.
 10. The method of controlling draw tension on thread according toclaim 1 wherein the step of controlling the at least one parametercomprises defining the bobbin so as to control frictional interaction ofthe bobbin and case that resists rotation of the bobbin relative to thecase with the bobbin operatively mounted on the case.
 11. The method ofcontrolling draw tension on thread according to claim 10 wherein thestep of defining the bobbin comprises selecting a material defining atleast a part of the bobbin.
 12. The method of controlling draw tensionon thread according to claim 10 wherein the step of defining the bobbincomprises providing a flexible component on the bobbin that is biasablyurged against the case with the bobbin operatively mounted on the case.13. The method of controlling draw tension on thread according to claim12 wherein the step of defining the bobbin comprises providing a surfacethat produces a frictional resistance to rotation when borne against bya flexible component on the case with the bobbin operatively mounted onthe case.
 14. The method of controlling draw tension on thread accordingto claim 1 wherein the step of controlling the at least one parametercomprises controlling the configuration of the bobbin.
 15. The method ofcontrolling draw tension on thread according to claim 1 wherein threadis wrapped around the bobbin with a wrapping pattern and the step ofcontrolling the at least one parameter comprises controlling thewrapping pattern.
 16. The method of controlling draw tension on threadaccording to claim 1 wherein thread is wrapped around the bobbin with awrapping tension and the step of controlling the at least one parametercomprises controlling the wrapping tension.
 17. A method of controllingdraw tension on thread wrapped around a bobbin and mounted operativelyon a case for movement relative to the case around an axis, the methodcomprising the steps of: providing a first bobbin with a supply ofthread wrapped around the first bobbin so that with the first bobbinoperatively mounted on a first case using a predetermined mountingprocess, a first thread draw tension results; providing a second bobbinwith a supply of thread wrapped around the second bobbin so that withthe second bobbin operatively mounted on the first case using thepredetermined mounting process, a second thread draw tension differentthan the first thread draw tension results; choosing a desired threaddraw tension by selecting to operatively mount to the first case one ofthe first and second bobbins; and operatively mounting the one of thefirst and second bobbins to the first case.
 18. The method ofcontrolling draw tension on thread according to claim 17 furthercomprising the step of predetermining approximately first and secondmagnitudes of thread draw tension resulting with each of the first andsecond bobbins operatively mounted on the first case using thepredetermined mounting process, and identifying the first and secondmagnitudes to facilitate selection by a user of one of the first andsecond bobbins for use.
 19. In combination: a first bobbin having asupply of a first thread wrapped around the first bobbin so that withthe first bobbin operatively mounted upon a case having a firstconstruction using a predetermined mounting process, a thread drawtension with a first magnitude results; and a second bobbin having asupply of a second thread wrapped around the second bobbin so that withthe second bobbin operatively mounted upon a case having the firstconstruction using a predetermined mounting process, a thread drawtension, with a magnitude of predetermined tension predetermined to begreater or less than the first magnitude, results, whereby the first andsecond bobbins with their respective thread supplies can be selectivelyoperatively mounted upon a case having the first construction to selectgreater or lesser thread draw tension.
 20. The combination according toclaim 19 further in combination with a first case having the firstconstruction upon which the first and second bobbins can beinterchangeably operably mounted.
 21. The combination according to claim19 wherein a difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction is attributable to atleast a difference in tack on the first and second threads.
 22. Thecombination according to claim 19 wherein a difference between a threaddraw tension resulting from the mounting of the first and second bobbinswith their respective thread supplies to a case having the firstconstruction is attributable to at least a difference in gauge of thefirst and second threads.
 23. The combination according to claim 19wherein a difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction is attributable to atleast a difference in material defining the first and second threads.24. The combination according to claim 19 wherein a difference between athread draw tension resulting from the mounting of the first and secondbobbins with their respective thread supplies to a case having the firstconstruction is attributable to at least a difference in shape of thefirst and second threads.
 25. The combination according to claim 19wherein the first and second threads are each defined by a plurality offibers and a difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction is attributable to atleast a difference in structural interaction of fibers defining thefirst and second threads.
 26. The combination according to claim 19wherein a difference between a thread draw tension resulting from themounting of the first and second bobbins with their respective threadsupplies to a case having the first construction is attributable to atleast a difference in magnetic interaction between a case having thefirst construction and the first and second bobbins.
 27. The combinationaccording to claim 19 wherein a difference between a thread draw tensionresulting from the mounting of the first and second bobbins with theirrespective thread supplies to a case having the first construction isattributable to at least a difference in a frictional interactionbetween a case having the first construction and the first and secondbobbins.
 28. The combination according to claim 19 wherein a differencebetween a thread draw tension resulting from the mounting of the firstand second bobbins with their respective thread supplies to a casehaving the first construction is attributable to at least a differencein configuration of the first and second bobbins.
 29. The combinationaccording to claim 19 wherein a difference between a thread draw tensionresulting from the mounting of the first and second bobbins with theirrespective thread supplies to a case having the first construction isattributable to at least a difference in wrapping pattern of the firstand second threads around the first and second bobbins.
 30. Thecombination according to claim 19 wherein a difference between a threaddraw tension resulting from the mounting of the first and second bobbinswith their respective thread supplies to a case having the firstconstruction is attributable to at least a difference in a wrappingtension for the first and second threads around the first and secondbobbins.
 31. The combination according to claim 19 wherein the firstbobbin has a first flange with a first peripheral edge and the secondbobbin has a second flange with a second peripheral edge each of whichedges faces a radially inwardly facing surface on a case having thefirst construction to which the first and second bobbins are operativelymounted, and a difference between a thread draw tension resulting fromthe mounting of the first and second bobbins with their respectivethread supplies to a case having the first construction is attributableto at least a difference in interaction of the first and secondperipheral edges with a radially inwardly facing surface on a casehaving the first construction to which the first and second bobbins areoperatively mounted.
 32. In combination: a case having a radiallyinwardly facing surface extending around a space; and a bobbin having anaxis and a first axially facing flange with a peripheral edge facing theradially inwardly facing case surface, wherein the case and bobbin areconfigured so that the peripheral edge does not contact the radiallyinwardly facing surface of the case around the entire peripheral edge.33. The combination according to claim 32 wherein the case and bobbinare configured so that the peripheral edge of the flange does notcontact the radially inwardly facing surface of the case.